Electron gun with nickel grid plate and copper-nickel alloy grid cylinder

ABSTRACT

An electron gun the first perforated electrode of which, which surrounds the cathode, consists of a perforated plate of nickel which is secured to a cylinder consisting of a copper-nickel alloy. (FIG. 3.

United States Patent Johannes Van Esdonk; Johannes Petrus Hornman, both of Emmasingel, Eindoven, Netherlands Inventors Appl. No. 34,650

Filed May 5, 1970 Patented Sept. 28, 1971 Assignee U.S. Philips Corp.

New York, N.Y.

Priority May 24, 1969 Netherlands 6908004 ELECTRON GUN WITH NICKEL GRID PLATE AND COPPER-NICKEL ALLOY GRID CYLINDER 3 Claims, 3 Drawing Figs.

U.S. Cl 313/311, 313/270 lnt.Cl H0lj 1/14, HOlj 1/48,H0lj 19/06 Field of Search 313/270,

lllnlllllll 'IIIIIII [56] References Cited UNITED STATES PATENTS 2,244,358 6/1941 Ewald 313/270 X 2,386,790 10/1945 Gaun et al. 313/270 X 2,393,057 1/1946 O'Larte et al... 313/85 2,431,137 11/1947 OLarte et a1 313/270X 2,468,136 4/1949 Taylor 313/356 2,611,676 9/1952 Pohle 316/23 Primary Examiner-David Schonberg Assistant Examiner-Toby H. Kusmer Attorney-Frank R. Trifari ABSTRACT: An electron gun the first perforated electrode of which, which surrounds the cathode, consists of a perforated plate of nickel which is secured to a cylinder consisting of a copper-nickel alloy. (FIG. 3.)

VIII/III)! VI/ II/IIIlI/IIII'I/l PATENTED SEP28 19?] INVENTORS JOHANNES VAN ESDONK JOHANNES P. HORNMAN BY 2M AGENT ELECTRON GUN WlTl-l NICKEL GRID PLATE AND COPPER-NICKEL ALLOY GRID CYLINDER The invention relates to an electron gun consisting of a cathode opposite to which a metal plate is provided, which plate comprises one or several apertures for passing an electron current and is secured to a metal cylinder.

It is found that upon heating during the formation of the cathode, the perforated plate often warps at the area of the perforation so that the distance from the perforation to the cathode surface changes. This is a drawback in particular if the distance between the cathode an the plate is very small (approximately I 4,). In such electron guns the permitted deviation usually is approximately percent, so :5 1., as is described also in U.S. Pat. No. 2,61 1,676, column 1, line 13.

An electron gun is known from the U.S. Pat. No. 2,468,136 in which the deformation of the plate serving as a first grid is avoided in that the plate is soldered to a metallized surface of a graphite cylinder by means of nickel-, molybdenumor platinum solder. However, the use of graphite is less desirable, since dust particles can be liberated thereby in the tube and the degasing will take a long time.

Furthermore it is known to provide a thin plate with a circumferential strengthening groove as is described in U.S. Pat. Nos. 2,393,057 and 2,61 1,676. lt is found, however, that if the material of the plate has a thickness of less than 200 a, said means in the known embodiments are no longer sufficient to prevent warping.

It has been found, however, that the deformation of such a plate can be avoided entirely if, according to the invention, the plate consists of nickel and the cylindrical part consists of a copper-nickel alloy. This alloy may contain from 40 to 75 percent by weight of nickel, but preferably an alloy is used of 55 percent by weight of copper and 45 percent by weight of nickel. The plate may be soldered to the cylinder, for example, by means of silver or be secured thereto by means of welding or diffusion. It has surprisingly been found that a nickel plate in a thickness of less than 200 p. remains entirely flat in the said combination of the materials.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which FIG. 1 is a cross-sectional view of a known embodiment of an electron gun after the heating,

FIG. 2 is a cross-sectional view of a Wehnelt cylinder of another known construction, while FIG. 3 is a cross-sectional view of a particular embodiment of an electron gun according to the invention.

Reference numeral 1 in FIG. 1 denotes the cathode support comprising the emitting layer 2 and a heater member 3. The Wehnelt electrode consists of a perforated plate 4 which is secured to a supporting cylinder 5. The plate 4 and the cylinder 5 consist both of chromium-nickel steel.

It has been found that the originally flat plate 4, after heating during the decomposition and formation of the cathode l, 2, is deformed as is shown in FIG. 1, so that the distance cathode-Wehnelt changes in spite of the presence of a circumferential 'groove 6.

The same is the case with the Wehnelt electrode 7 shown in F IG. 2 which consists entirely of chromium-nickel steel.

In FIG. 3 the perforated plate 9 consists of nickel, the supporting cylinder 8 of a copper-nickel alloy with 55 percent by weight of copper and 45 percent by weight of nickel. The plate 9 is soldered to the cylinder 8 by means of silver. The plate 9 also comprises a circumferential groove 6. The groove 6 is from the scope of the present invention.

What IS claimed is:

1. An electron gun comprising a cathode opposite to which is placed a metal plate having at least one aperture for passing an electron current, which plate comprises a circumferential strengthening groove and is secured to a metal cylinder, characterized in that the perforated plate consists of nickel having a thickness less than 200 p. and the cylinder consists of a suitable copper-nickel alloy.

2. An electron gun as claimed in claim 1, characterized in that the copper-nickel alloy of the cylinder is from 40 to 75 percent by weight of nickel.

3. An electron gun as claimed in claim 1 characterized in that the cylinder consists of an alloy of 55 percent by weight of copper and 45 percent by weight of nickel. 

2. An electron gun as claimed in claim 1, characterized in that the copper-nickel alloy of the cylinder is from 40 to 75 percent by weight of nickel.
 3. An electron gun as claimed in claim 1 characterized in that the cylinder consists of an alloy of 55 percent by weight of copper and 45 percent by weight of nickel. 